1. Field of the Invention
This invention relates to a linear motion guide unit suitable for use in environments where foreign substances are likely to be encountered, such as in a machine tool.
2. Description of the Related Art
FIG. 4 to FIG. 8 show an example of related-art linear motion guide units, which includes a guide rail 1 and a slider 2 straddling and sliding on the guide rail 1. The slider 2 has end caps 2a respectively attached to two opposing ends of the slider 2. Rolling elements 3 change in travel direction in the end caps 2a while traveling through the same. As illustrated in FIG. 5, the rolling elements 3 travels along a guide rail 1 provided on the slider 2 while rolling on a guiding face 1a of the guide rail 1. The rolling elements 3, raceways for guiding the rolling elements 3 and allowing the rolling elements 3 to change in travel direction, and the like form a sliding mechanism M.
The slider 2 thus structured is provided with an inner sealing member 4 which extends on an inner surface facing a flat surface 1b of the guide rail 1 in the longitudinal direction of the guide rail 1. The inner sealing member 4 has two opposing sides extending in the longitudinal direction of the guide rail 1. The two sides are folded back to form lips 4a extending inward. The lips 4a are in contact with the flat surface 1b of the guide rail 1 to prevent foreign substances adhering to the flat surface 1b from entering the sliding mechanism M.
Bottom sealing members 5 are also mounted on the underside of the slider 2 to extend in the longitudinal direction of the guide rail 1. The bottom sealing members 5 are in contact with the side faces 1c of the guide rail 1 to prevent foreign substances from entering the sliding mechanism M from the outside.
Rubber-made end seals S each including a built-in wiper seal 6 and a built-in sealing plate 7 which are shown in FIG. 6 are respectively attached to the outer end face of the end caps 2a of the slider 2. Scrapers 8 are respectively affixed to the outer end faces of the end seals S.
In the linear motion guide unit structured in this manner, during the reciprocation of the slider 1, the scrapers 8 removes foreign substances from the guide rail 1, then the wiper seals 6 and the end seals S prevent the small foreign substances slipping through the scrapers 8 from entering the inside of the slider 2.
As seen from FIG. 6, each of the end seals S structured in this manner includes a lip 9 which is in contact with the guide rail 1. The lip 9 has an inclined face 9b formed closer to the end cap 2a in order to form a contact corner 9a for making contact with the guide rail 1.
The contact corner 9a is provided in the lip 9 for the purpose of reducing the contact area of the lip 9 with the guide rail to reduce the sliding resistance of the slider 2 in order to prevent the lip 9 from being caught.
An example of such linear motion guide units is described in JP-A-2008-281091.